A Storage Area Network (SAN) is a specialized network which enables access among servers and storage resources available on the network. Thus SAN's enable a number of servers and their applications to transfer and move large amounts of data. A major advantage of the SAN configuration is that communication via the SAN is specific to data storage operations, i.e. the data storage related traffic is not shared with other general purpose traffic. The resultant independence of storage related traffic in the SAN provides a more efficient means of carrying out required storage operations. A typical SAN configuration, however, provides only one controller per media storage type. For example, an HDD media has its controller while tape or other removable media unit has a different controller with no data communications linking the two controllers. The lack of linkage between the two controllers results in storage/retrieval bottlenecks when either controller or media system is unavailable to service a request from any of the hosts. A solution to this problem would make a SAN more robust and increase the desirability of using a SAN, especially for Hierarchical Storage Library systems and the like.
The prior art does not address the problem of concurrent storage and retrieval of diverse media. Existing systems, such as disclosed in Keele, (U.S. Pat. No. 5,455,926), provide tape emulation where the media is actually a HDD or optical storage unit, however no mechanism is provided for alternative operation as a primary or secondary failover storage media in a SAN as required in the instance of a controller/media failure or busy status indication.
Yet another reference, Tzelnic et al (U.S. Pat. No. 5,829,046), discloses dual redundant controller servers for robotic commands to a tape library. This reference, however does not solve the additional problem of protocol conversion for concurrently maintaining storage access in both HDD and tape or other storage systems with diverse media.
It would thus be highly desirable to provide a robust storage media and control system wherein data storage communication with a host system continues seamlessly despite controller/media failure or busy status.